What is Pharmacogenomics?

You inherit your genetic code from your ancestors. That means that many of the changes in your DNA that affect your response to a drug are shared with your family, including your parents and your children. Some of the genetic variation that causes differences in medicine response are found more commonly in people of certain ancestries or ethnicities than in others.

However, your ancestry can only suggest how likely it is that you will have a particular change in your DNA – you will still need to have a genetic test to confirm that the change is indeed in your DNA. Therefore, if you are curious about how your DNA might affect your response to a medicine, you should get a pharmacogenomic test.

Transporters move molecules in and out of cells. Variation in genes encoding drug transporters can affect their function, changing how well drugs can enter or exit cells and increasing or decreasing concentrations of a drug in different parts of the body. If the concentration of the drug at the site of action is too low, the drug may not work as well. If the drug concentration becomes too high, it could cause toxic side effects.

Variation in drug metabolizing enzymes can affect how quickly a drug is broken down in the body. This can have different effects depending on the specific drug. If an active drug is metabolized too quickly, it will be inactivated too quickly and may not work well. If it is metabolized too slowly, toxic concentrations of the drug might build up. Alternatively, some drugs have to be metabolized in order to become active. For drugs like these, being metabolized too quickly increases the concentrations of active molecules in the body and increases the risk of toxic side effects while being metabolized too slowly can reduce how effective the drug is.

HLA proteins form part of your immune system. Some HLA alleles are associated with increased risk for an allergic response to certain medications, which can result in severe skin reactions such as Stevens-Johnson syndrome (SJS)(opens in new window) or toxic epidermal necrolysis (TEN)(opens in new window).

Variation in genes coding for proteins which are drug targets can affect how well a drug works by altering the amount of the target protein in the body or by preventing the drug from being able to bind to the protein. For example, the anti-coagulant drug warfarin(opens in new window) prevents the vitamin K recycling needed for blood clotting. Warfarin does this by blocking the protein that controls the recycling (VKORC1). Genetic variation that increases or decreases the amount of VKORC1 can affect the dose of warfarin needed to prevent blood clotting.